Process of producing integral color correction masks



Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to colouring processes and more particularly tocolouring processes for use in colour photography.

The dyestuffs and pigments used in practice in subtractive processes ofcolour photography do not possess ideal special absorption curves. Inaddition to absorbing light in the desired part of the spectrum theyalso absorb somelight in other parts of the spectrum and in consequencethe colour reproduction obtained is never ideal. For example magentadyestufis formed by colour development absorb the desired complementarycoloured green light and in addition always absorb undesirably a certainamount of blue light. It has been proposed (see for example The Journalof the Photographic Society of America, volume 13, 94-96, February 1947)to correct for these deficiencies by the use of an automatic maskingmethod whereby coloured colour formers are used, the light absorption ofthe coloured colour former being equal or approximately equal to theundesired light absorption of the developed dyestufi. For example thecolour former which is used in a photographic layer to form a magentadyestufi on colour development may itself be coloured yellow so that itabsorbs blue light at an intensity equal to the undesired blueabsorption of the magenta dyestufi" formed by colour development.Accordingly the unchanged colour former itself forms the coloured maskand the blue absorption of the photographic layer is a constant value(irrespective of the green absorption of the magenta image) which can becompensated for by using a suitable filter when printing.

The coloured colour formers it has been proposed to use in the aboveprocess are compounds containing the group -N=NR where R is an aromaticor heterocyclic radical. The

N=NR

group is'split off during the development with an aromatic aminocompound and replaced by the phenylimino radical derived from thearomatic amino compound. Apart from the'difiiculties caused by the useof a coloured layer, particularly in multidayer films, the mainpractical objection to the above automatic masking process lies in thefact that the reaction of coloured colour formers of this kind with thearomatic amino compounds used for development is usually much slowerthan the reaction of the normal colourless colour formers with thearomatic amino compounds.

We have now discovered a new masking process PROCESS OF PRODUCINGINTEGRAL COLOR CORRECTION MASKS Karl Otto Gauguin and Norman HultonHaddock,

Blackley, Manchester, Imperial Chemical Indu ration of Great Britain NoDrawing. Application August 1, 1949, Serial No. 108,045

Claims priority, application Great Britain August 20, 1948 England,assignors to stries Limited, a corpovolved in using this kind ofcoloured colour former. In our new masking process we use colourlesscolour formers, the yellow colour former being of a particular kind, andafter developing the image with a colour iormingdeveloper, we treat thefilm with a gelatine hardening agent so that the residual colour formerin selected parts of the film is rendered incapable of coupling with adiazonium compound, and subsequently we treat the film with a diazoniumcompound so that the residual colour former, which is still capable ofcoupling, is converted into the desired colour masks.

According to our invention we provide an improved process for colourphotography which comprises developing with a colour forming develope anexposed multilayer film wherein there is present in at least one of thelayers, a yellow colour former which contains in its molecular structurethe grouping COCI-I2CO as part of an open chain of atoms, treating thefilm with a gelatine hardening agent, and subsequently treating the filmwith a solution of a diazonium compound.

The process of our invention is particularly valuable for use in threecolour subtractive processes of colour photography in which there areused multilayer films which contain yellow, magenta and cyan colourformers in three separate layers, and in which the colours are formed bydeveloping the films with alkaline solutions of aromatic aminocompounds, such as for example p-diethylaminoaniline. In suchprocesses'to improve the fidelity of colour reproduction, a colour maskis required in the magenta layer, (that is the layer containing themagenta colour former)v to correct for the imperfect colour absorptionof the magenta dyestuff, and to a smaller extent in the cyan layer, tocorrect for the imperfect colour absorption of the cyan dyestuff, but nomask is usually required in the yellow layer. In the process of ourinvention the film after colour development contains residual colourformer which is capable of reacting with a diazonium compound to form acolour mask but after treating he film with a gelatine hardening agent,the yellow colour formers of the kind hereinbefore defined, present inthe yellow layer of the film, are unable to react with the diazoniumcompound and accordingly no mask is formed in the yellow layer. Thiseffect is a general efifect obtained with different kinds of gelatinehardening agents. This efiect is not completely understood but itappears to be associated with the 2,663,637 i v m overall hardening ofthe yellow layer containing the specified colour former.

As examples of yellow colour formers suitable for use in the process ofthe present invention, there may be mentionedp-stearoylaminopenzoylacetanilide-p -carboxylic acid,p-methoxybenzoylaceto (2 N octadecyl a N methylamino) -carboxyanilide,p-stearoylaminobenzoylacetamlide-3:5-dicarboxylic acid.

The quantities of colour formers originally introduced into the magnetalayer and the cyan layer may, if desired, be so adjusted that afterexposure and colour development there is very little or no residualcolour former in these layers in the areas of maximum exposure so thatlittle or no colouring matter is formed in these areas of maximumexposure on treating the film with a solution of a diazonium compoundand accordingly the overall fog of the masking image is reduced to aminimum. This forms a further feature of our invention. When thequantities of colour former are so adjusted, the treatment of the filmwith a hardening agent may be carried out before, during or after thebleaching of the silver, and any gelatine hardening agents, for examplecompounds of aluminum or chromium, can be used. For example there may beused potassium alum or chrome alum or there may be used the hardeningagents used for the imagewise tanning of gelatine in the so-calledCarbon, Carbro, Collotype, Bromoil or Transfer processes (see forexample History of Color Photography by J. S. Friedman, 1947, publishedby The American Photographic Publishing Company, Boston) Alternativelythe fog of the masking image can be controlled by carrying out thehardening treatment simultaneously with the bleaching out of the silver,that is to say by treating the film after exposure and colourdevelopment with a tanningbleaching bath. This forms a still furtherfeature of our invention. Examples of such tanningbleaching baths arefor example described in History of Color Photography by J. S. Friedman,1947, pages 466, 467 and Q68.

In this modification of the process all the residual yellow colourformer is rendered incapable of coupling but seemingly in the magentalayer and cyan layer only imagewise hardening occurs since on treatingthe film with a solution of the diazonium compound coupling occurscounter-imagewise in these layers. In this modification of the processtherefore it is unnecessary to adjust the quantity of colour formersincorporated in the emulsions in order to ensure that the colour formeris substantially used up in the areas of maximum exposure.

The density and gradation of the masking images formed in the processcan be controlled by adjusting the concentration and temperature of thesolution of diazonium compound used in the process. The relative densityand gradation of the masking images in the magenta layer and the cyanlayer can be controlled by adjusting the relative concentration andnature of the colour formers used in the two layers. Alternatively therelative densities and gradation of the two masking images can becontrolled by using as colour former in the cyan layer a mixture of acolour former of the i-naphthol series with the 4- positionunsubstituted, and a colour former of the l-naphthol series with asubstituent in the 4-position. This substituent in the 4-positi0nprevents coupling with a diazoniuin compound but does not preventreaction with the aromatic amino compound used as colour-formingdeveloper and this forms still a further feature of our invention. Forexample there may be used a mixture of the p- (methyl-octadecyl-amino)-anilide of l-hydroxy- 2-naphthoic acid and of the corresponding42-5111- phonic acid. The unsulphonated colour former will react eitherwith the colour forming developer or with the diazonium compound but thesulphonated colour former will react only with the colour formingdeveloper and not with the diazonium compound.

The diazonium compounds chosen for use in the formation of the maskingimages should be such as will react with the residual colour formers togive azo dyestuiis having the light absorption properties required tocompensate, as far as possible, for the undesirable light absorption orthe dyestuffs formed by the normal colour development with aromaticamino compounds. The solutions of the diazonium compounds may beprepared by diazotising the parent bases or alternatively they may beprepared from any available form of stabilised or passive diazoniumcompound (see for example The Aromatic Diazo Compounds by K. H. Saunderspublished by Edward Arnold & Co., London, 1936).

The process of our invention may be used to obtain positive maskingimages alongside the normal negative images obtained by simple exposureand colour development or alternatively it may be used in associationwith reversal processes so that negative masking images are obtainedalongside the normal positive images and this forms a still furtherfeature of our invention. For example the multilayer film may be firstexposed to the light from an object or to the light transmitted by acolour transparency, developed with a black and white developer, the

developed silver re-bleached to silver chloride.

and the latter dissolved out with, for example,

sodium sulphite solution which does not affect.

the residual silver bromide. The film may then be fully exposed to lightand subsequently processed by developing with a colour formingdeveloper, bleach-tanning, treating with a diazonium compound andfixing. Alternatively if the quantities of colour formers in the magentalayer and cyan layer have been suitably adjusted, the film may beexposed to the image or to the light transmitted by a colourtransparency, developed with a black and white developer, re-exposed anddeveloped with a colour forming developer, tanned, treated with adiazonium compound, bleached and fixed.

The invention is illustrated but not limited by I the following examplesin which the parts are by weight.

EXAlVEPLE 1 A multilayer light sensitive photographic film is made up asfollows:

A support material is coated with a layer or" red light sensitisedemulsion containing 10 grams per litre of the cyan image producingcolour coupler described in Example 10 of British specification No.465,823. Upon this layer there is coated a green light sensitisedemulsion containing 10 grams per litre of the magenta image producingcolour coupler described in Example 3 of British specification No.502,665. A layer of colloidal silver is now coated on to act as a filterlayer, and finally a layer of unsensitised emulsion containing 10 gramsper litre of the sodium salt of p-stearyl-aminobenzoylacetanilide-p'-carboxylic acid. The film is exposed to access-vi lightand developed in the developere'made up: by

the: following recipe. p-diethylaminoaniline hydrochloride The film isrinsed and transferred into a tanning-bleaching bath made up by mixing,equalparts of the following Solutions A and B.

Solution A Parts Potassium ferricyanide 37.5 Potassium bromide 36.25Potassium dichromate 3-7.5 Acetic acidr". 10.0 Water to 1000 Solution BParts Potassium alum 50 Water to 10 The film is washed. again,thentreatedwith a 1% solution of the zinc chloride double salt ofp-nitrobenzene diazonium chloride, washed and finally fixed with a 20%solution of sodium thiosulphate.

After this treatment the red sensitive layer contains a cyan dyestuffnegative image and also a red azo dyestufl positive image which servesas a mask to correct for the undesirable absorption of blue and greenlight by the cyan dyestuff.

The green sensitive layer contains a magenta EXAMPLE. 2

The material is exposed to light transmitted" by a colour negative orpositive transparency and developed in the developer made up by thefollowing recipe:

Grams Sodium sulphite anhydrous 25 Metol 2' Hydroquinone 14 Potassiumbromide 2 Potassium thiocyanate 2.5 Sodium hydroxide 2 Potassiumcarbonate 4011 Sodium. sulphate anhydrous 10 Water.. 1000' Afterwashing, the film is transferred into a bleaching solution made up bythe following recipe: 7

Potassium ferricyanide grams- Sodiumchloride .do 50 Water cc 1000 Thedeveloped silver is thus bleached tosilver chloride. The film is thentreated with a: 20%. solution of sodium sulphite which dissolves thesilver chloride, but leaves the residual silver bromide unafiected.

The material is now exposed to the light from a tungsten lamp, developedin the colour developer of Example. 1 and then further processed asdescribed in Example 1. Instead of the di'azo compound used in Example1, the diazonium compounds derived from l-nitro-fi-methoxy aniline,e-methoxy-fi-nitroaniline, e-aminodiphenylamine,4-benzoylami'no-6-methoxyani1ine or any other diazonium compounds whichcouple with colour formers to give the colours needed for maskingpurposes may be used.

The processed film contains in the red sensitive layer a cyan dyestuffpositive image and a red dyestufii negative image, which. serves as amask to correct the too low transmission of blue and green light by thecyan dyestuff. The green sen sitive' layer contains a magenta. dyestufipositive.

image and a yellow dyestuff negative image, which. serves as a mask tocorrect for the absorption of blue light by the magenta dyestuff.

The blue sensitive layer contains a yellow dyestuff positive image butno corresponding azo dyestufi negative image. The negative or positivedupe prints so obtained show improved colour fidelity and brightnesscompared with dupe prints made without colour correction masks.

EIMMPLE 3 A multilayer light sensitive. material is made up as follows:

A support material is coated with a layer of red light sensitiveemulsion containing 6 grams per litre of the sulphonated condensationproduct described in. Example 10 of British'specification No. 465,823and 2 grams per litre of the corre-- sponding unsulphonated.condensation product.

Upon. this layer is coated a ee light Sensitised emulsion containing 4grams per litre of the magenta. image producing colour couplerdescribed. in Example 3 of British specification No; 502,665. Acolloidal silver layer is now coated on to act as a yellow filter layerand as the top layer an unsensitised emulsion is coated containing 10'grams per litre of the sodium salt of pstearyl. aminobenzoylacetanilidep-carboxylic acid;

The material is exposed to light and developed with the. colourdeveloper used in Example 1. Alter-washing, the film is treated with aharden ing bath. containing 2.5% potassium chrome alum. The film iswashed again and trans ferred to a bleaching bath of the followingcomposition:

The film is washed. and soaked. inv a 1% solutionofithe zinc chloridedouble salt of 2-methtive obtained in Exampl 1.

EXAMPLE 4 A multilayer film is made up as described in Example 3.

After exposure to light the film is developed with the black and whitedeveloper used in Example 2, and after washing and reexposure it isdeveloped in the colour forming developer used in Example 1. Then thematerial is hardened in the hardening solution made up according to thefollowing recipe:

Potassium alum grams 39 Sodium acetate do 60 Water cc 1000 Acetic acid,glacial ce 5 The film is transferred into a 1% solution of the zincchloride double salt of Z-methoxylnitrobenzene diazonium chloride. It isthen bleached, fixed and finally washed.

The transparency obtained is of the reversal type and has features andimprovements similar to those of the transparency obtained in Example 2.

EXAMPLE 5 A multilayer light sensitive material is made up as follows:

A support material is coated with a layer of red light sensitizedemulsion containin grams per litre of the sodium salt ofl-hydroxy--sulphonaphthoyl (2) -octadecylamide. Upon this layer iscoated a green light sensitized emulsion containing 1o grams per litreof the 1t3-bis-( 8- cyanoacetyl)-5octadecylamino benzene. A colloidalsilver layer is now coated on and as the top layer an unsensitisedemulsion is coated containing 19 grams per litre of the sodium salt of pstearylaminobenzoylacetanilide-pcarboxylic acid. The material is exposedto light and developed with the colour developer used in Example l. Thefilm is washed and then treated with the hardening solution used inExample 4.

The film is washed and then transferred to the bleaching bath used inExample 4.

The material is again washed and then immersed in a 9.5% solution of thezinc chloride double salt of 2-nitro-l-methoxy-benzene diazoniumchloride, and finally fixed and washed. The colour negative obtainedcarries a cyan negative image in the layer next to the support, amagenta negative image and a yellow azo dyestuff positive masking imagein the next layer, a clear gelatin layer left after bleaching of thecolloidal silver, and finally a yellow negative image in the upperlayer.

We claim:

1. A process for the production of subtractively colored photographictransparencies with color correction masks from multi-layer film havingdifferently sensitized silver halide emulsion layers containing colorformers adapted to form yellow,

magenta, and cyan images in separate layers by coupling with thedevelopment product of a primary aromatic amino developing agent andbeing capable of producing azo dyes by coupling with a diazoniumcompound, wherein the color former which is adapted to form a yellowimage contains in its' molecular structure the group --CO--CH2CO-- aspart of an open chain of atomsjwhich comprises exposing the film tolight, color developing to said color images by treating said layerswith said primary aromatic amino developing agent, treating the filmwith a gelatin hardening agent selected from the group consisting ofchromium and aluminum gelatin hardening compounds to render the residualcolor former in the yellow image layer incapable of coupling with adiazonium compound, subsequently treating the film with a solution of adlazonium compound to convert residual color former in the magenta andcyan colored layers into masking images and retaining the color imagesand masking images in said layers.

2. A process for the production of subtractively colored photographictransparencies as set forth in claim 1 wherein said color formercontaining in its molecular structur the group as part of an open chainof atoms is selected from the group consisting ofp-stearoyl-aminoloenzoylacetanilide-p-carboxylic acid,p-methoxy-benzoyiacetc (2-l i-octadecyl-N-methylamino) 5-carooxyanilide, and p-stearoylaminobenzoylacetani1ide-3 5-dicarboxylicacid.

3. A process for the production of subtractively colored photographictransparencies as set forth in claim 1 wherein the quantities of magentaand cyan color formers in said difierently sensitized silver halideemulsion layers are so adjusted that after exposure and colordevelopment there is substantially no residual magenta or cyan colorformer in the areas of maximum exposure of their respective layers.

4. A process for the production of subtractively colored photographictransparencies as set forth in claim 1 wherein the treatment with thegelatin hardening agent is carried out simultaneously with the bleachingout of the developed silver.

5. A process for the production of subtraetively colored photographictransparencies as set forth in claim 1 wherein the cyan color former isa mixture of a color former of the l-naphthol series with the 4-positionunsubstituted and a color former of the l-naphthol series with asubstituent in the it-position.

6. A process for the production of subtractively colored photographictransparencies as set forth in claim 1 wherein prior to color developingto said color images, the multi-layer film is first exposed to light,developed with a black and white developer, bleached, and then fullyexposed to light.

KARL OTTO GANGUIN. NORMAN HULTON HADDOCK.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR THE PRODUCTION OF SUBSTRACTIVELY COLORED PHOTOGRAPHICTRANSPARENCIES WITH COLOR CORRECTION MASKS FROM MULTI-LAYER FILM HAVINGDIFFERENTLY SENSITIZED SILVER HALIDE EMULSION LAYERS CONTAINING COLORFORMERS ADAPTED TO FORM YELLOW, MAGNETA, AND CYAN IMAGES IN SEPARATELAYERS BY COUPLING WITH THE DEVELOPMENT PRODUCT OF A PRIMARY AROMATICAMINO DEVELOPING AGENT AND BEING CAPABLE OF PRODUCING AZO DYES BYCOUPLING WITH A DIAZONIUM COMPOUND, WHEREIN THE COLOR FORMER WHICH ISADAPTED TO FORM A YELLOW IMAGE CONTAINS IN ITS MOLECULAR STRUCTURE THEGROUP -CO-CH2CO- AS PART OF AN OPEN CHAIN OF ATOMS, WHICH COMPRISESEXPOSING THE FILM TO LIGHT, COLOR DEVELOPING TO SAID COLOR IMAGES BYTREATING SAID LAYERS WITH SAID PRIMARY AROMATIC AMINO DEVELOPING AGENT,TREATING THE FILM WITH A GELATIN HARDENING AGENT, SELECTED FROM THEGROUP CONSISTING OF CHROMIUM AND ALUMINUM GELATIN HARDENING COMPOUNDS TORENDER THE RESIDUAL COLOR FORMER IN THE YELLOW IMAGE LAYER INCAPABLE OFCOUPLING WITH A DIAZONIUM COMPOUND, SUBSEQUENTLY TREATING THE FILM WITHA SOLUTION OF A DIAZONIUM COMPOUND TO CONVERT RESIDUAL COLOR FORMER INTHE MAGENTA AND CYAN COLORED LAYERS INTO MASKING IMAGES AND RETAININGTHE COLOR IMAGES AND MASKING IMAGES IN SAID LAYERS.